1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for coating and/or cleaning seismic equipment that is deployed in water or underwater.
2. Discussion of the Background
During the past years, interest in developing new oil and gas production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel. Offshore drilling is an expensive process. Thus, those engaged in such a costly undertaking invest substantially in geophysical surveys to more accurately decide where to drill in order to avoid a dry well.
Marine seismic data acquisition and processing generate a profile (image) of the geophysical structure (subsurface) under the seafloor. This profile is used by those trained in the field to evaluate the presence or absence of oil and/or gas traps. Thus, providing a high-resolution image of the subsurface is an ongoing process for the exploration of natural resources, including, among others, oil and/or gas.
During a seismic gathering process, as shown in FIG. 1, a vessel 10 tows an array of seismic detectors provided on streamers 12. The streamers may be disposed horizontally, i.e., lying at a constant depth relative to a surface 14 of the ocean. The vessel 10 also tows a sound source assembly 16 that is configured to generate an acoustic wave 18. The acoustic wave 18 propagates downward, toward the seafloor 20, and penetrates the seafloor until eventually a reflecting structure 22 (reflector) reflects the acoustic wave. The reflected acoustic wave 24 propagates upward until it is detected by a detector on streamer 12.
The above-noted arrangement is towed underwater for days, if not weeks, for a given survey. Thus, it was noted that various marine creatures or animals, e.g., barnacles, attach to various components of the streamer, e.g., external skin, electronic components, birds, etc. The barnacles may increase the drag on the streamer, which increase fuel consumption and may damage the equipment, or they may change the desired weight of the streamer, may make the streamer deviate from its desired towed position, may affect the recorded signal, may introduce noise or simply may make it difficult to manipulate the streamer for maintenance or when deployed underwater.
Traditional methods employ a cleaning device configured to move along the streamer and clean the streamer of marine animals. However, there are problems with these devices because they are bulky and they need to travel along various elements (e.g., birds, electronic boxes, etc.) connected to the streamer.
An improved method is disclosed in U.S. Provisional Patent Application Ser. No. 61/657,511 ('511 herein), assigned to the same assignee as the present patent application. FIG. 2, which corresponds to Figure of '511, shows a cleaning device 200 that is deployed over (around) a streamer 202 for providing one or more functions (e.g., cleaning, repairing, etc.) to the streamer. The streamer 202 extends into the water and is towed by a vessel (not shown) along direction X. The cleaning device 200 has a body 204 made of a flexible material, e.g., composite, plastic, metal or a combination thereof. The body 204 has a spiral-type shape and may be wrapped around the streamer 202. The body 204 preferably is able to twist one portion relative to another portion, i.e., it is flexible for reasons to be discussed later. Thus, the body 204 may have a spring shape as shown in FIG. 2 and is capable of compressing or extending depending on the applied forces.
For making the cleaning device 200 advance along the streamer 202 (along direction 210), a movement-generating device 206 is provided at one end 208 of the body 204. The movement-generating device 206 may be an anchor or a surface configured to be acted upon by the water while the streamer is towed with a given velocity so that the cleaning device 200 is drag-propelled while the streamer is towed.
For providing rotational motion to the body 204, or for supplementing the rotational motion, wings 220 may be provided along the body 204. The wings 220 are oriented relative to the body 204 so that due to the motion of the streamer along direction X, the water acts on the wings 220 to rotate them and implicitly the body 204 along the rotational direction 212. The cleaning device 200 may have various elements to provide desired functions, e.g., cleaning, repairing, etc.
However, one or more components of the above described system may become blocked, e.g., when passing a bird, and thus, may fail to achieve the intended use.
Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.